<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>导航栏</title>
</head>
<body>
    <div class="parent">
        <div class="nav">我是导航栏</div>
        <div class="body">
            <div class="left">我是左边栏</div>
            <div class="content">我是内容区</div>
            <div class="right">我是右边栏</div>
        </div>
    </div>
    <style>
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
 
 
        .parent {
            background-color: gray;
        }
 
 
        .nav {
            background-color: red;
            color: white;
            text-align: center;
            height: 50px;
            line-height: 50px;
            font-size: 20px;
        }
 
 
        .body {
            display: flex;
        }
 
 
        .left, .right {
            width: 20%;
            height: 500px;
            background-color: green;
            font-size: 20px;
            color:white;
            line-height: 500px;
            text-align: center;
        }
        
        .content {
            width: 80%;
            height: 500px;
            background-color: gray;
            font-size: 20px;
            color:white;
            line-height: 500px;
            text-align: center;
        }
    </style>
</body>
</html>